What's a good adjective to describe a smile which is not genuine, but still has a good connotation?
I was thinking of using fake smile, but fake has a negative connotation, which I'm trying to avoid. In fact, I'm looking for something that says the exact opposite about the person... they aren't trying to be fake towards people, they are just so kind that they don't want the other person to feel bad, therefore they put on an insincere smile to be kind towards them. Insincere, too, has a negative connotation which I'm trying to avoid, since it makes the person sound like they have negative qualities as well.
Perhaps a little background could help clarify: imagine a person that is annoyed by something that a friend does, but doesn't want the friend to feel bad about annoying her, so she puts on a smile just for show. The smile isn't meant to be [snarky, rude, disparaging, sarcastic, etc.], it is truly, genuinely meant to be so that the other person doesn't feel bad about annoying her. Therefore, as you can see, the person really is kind and using a word such as fake doesn't do justice to describe the smile.